Area Calculator
Area of rectangle, circle or triangle.
How to use Area Calculator
Compute the area of a rectangle, circle or triangle from its dimensions.
Open Area Calculator on toolpermarket and fill in the inputs the tool asks for.
In the Dimensions field, enter length and width (or radius for a circle). Keep both in the same unit.
In the Shape field, pick rectangle, square, or circle. Circles need the radius, half the diameter.
Press Calculate to compute the result. The output appears immediately below the form. Adjust the inputs and recalculate as many times as you need.
Read the result and use it as needed. If the number looks off, re-check your inputs and run it again — the math is deterministic, so the same entries always return the same answer.
Worked example. A 5 m by 4 m rectangle is 20 square meters; a circle of radius 3 m is about 28.3 square meters.
Tips for accurate results.
Square units, not plain units, are the answer.
For a circle use radius; halve the diameter first.
Match units before comparing two areas.
When to use Area Calculator. Estimating flooring, paint, or tiling needs. Sizing a garden bed or room. Checking a quoted area against your own measure.
When you actually reach for this
- You need the area of a room, plot or shape for flooring, paint or land.
- You are converting between square units (ft2, m2, acres).
Where this tool stops being accurate
- It uses the standard shape formulas; irregular lots need splitting into simpler shapes.
- Irregular or curved boundaries are approximated, not survey-accurate.
Frequently asked questions
Why is area in square units, not meters?
Area is two-dimensional, so the unit is length times length — square meters, square feet. A 5 by 4 space is 20 of those squares. Forgetting the "square" is the common slip that makes an area sound like a length.
Do I enter diameter or radius for a circle?
Radius — the distance from center to edge. If you only have the diameter, halve it first. Using the full diameter in the formula overstates the area by four times, which is a frequent mistake.
Can I mix meters and feet in one shape?
Not directly. Convert both dimensions to the same unit first, or the area is wrong by the square of the conversion factor. The tool assumes consistent units, so do the conversion yourself before entering.
How do I area a weirdly shaped room?
Break it into rectangles and triangles, compute each, then add them. The tool handles the simple shapes; you sum the pieces.